The present invention relates to a method of preparing an aerosol suppressant composition and to the use of the composition to reduce or suppress silicone mist in high speed coating processes and significantly increase the adhesion of the coating to the substrate. More particularly, the present invention relates to a method of preparing an aerosol suppressant composition by reacting an organosilicon compound, an oxyalkylene containing compound, and a catalyst. The composition, when added to curable silicone coatings, reduces the amount of silicone mist in high speed coating processes.
One of the current trends in the silicone coating industry is trying to operate coating machinery as fast as possible to increase productivity. As silicone materials are applied to a substrate at very high speed such as 1000 to 1500 ft/min the coating material tends to form a "mist" which comprises very fine particles blown out from the coating head. Recently this phenomenon has become one of the most serious problems in the industry. Although the coating materials are capable of fast thermal cure or are even radiation curable, presently they cannot be coated at high speed due to the misting problem.
Another trend in the silicone coatings industry is to use plastic films such as polyolefins and polyesters as a substrate for the curable coating which requires that the silicone coating anchors to the plastic film. To obtain good anchorage on the films has in the past required curing at higher temperatures at slow curing rates. Thus fast cure formulations could not be applied to plastic films due to the aforementioned problems. Furthermore, since plastic films cannot tolerate high temperatures during the coating process only very limited applications exist which can employ plastic films as substrates for coatings. The present invention is directed at solving these problems.
Organosilicon compounds containing oxyalkylene functionality have been described in the art. For example, in Great Britain Patent Specification No. 0981811 there is disclosed a siloxane-oxyalkylene block copolymer useful in the preparation of cellular materials which are prepared by reacting a polyalkylene glycol containing as one terminal group carbamidoalkyl radicals or sulphonamidoalkyl radicals with a hydrocarbonoxy polysiloxane preferably in the presence of an alkali hydroxide or alkali metal salt catalyst. Jack et al. in U.S. Pat. No. 3,478,075 disclose terpolymers which contain at least one polysiloxane block, at least one polyoxyalkylene block, and at least one block selected from polyvinylester and partially and wholly hydrolysed polyvinylesters useful as surfactants or cell control agents in polyurethane foam systems which are prepared by a variety of methods.
Litteral et al. in U.S. Pat. No. 4,025,456 disclose a process for preparing siloxane-oxyalkylene copolymers which includes a hydrosilylation reaction between an organohydrogenpolysiloxane reactant and an olefinically substituted polyoxyalkylene reactant which may be conducted without a solvent or conducted in an oxygen containing solvent such as an ether, a polyether, or a lower or higher molecular weight alcohol.
Mehta et al. in U.S. Pat. No. 4,847,398 disclose a process for the preparation of siloxane-oxyalkylene copolymers in an essentially solventless system which comprises forming a mixture of an organohydrogensiloxane, a polyoxyalkylene compound, and a carboxylic acid or a carboxylic acid salt as a reaction promoter, adjusting and maintaining the temperature of said mixture to a temperature to promote the reaction of said organohydrogensiloxane with said polyoxyalkylene, adding to said mixture a catalytic amount of a noble metal hydrosilylation catalyst, allowing said reaction to go to completion, and recovering said copolymer.
Another process for preparing siloxane-oxyalkylene copolymers is described in Austin et al., U.S. Pat. No. 4,857,583 which discloses a process for preparing organosiloxane copolymer surfactants in a saturated, polar, high boiling point polyol solvent which comprises forming a mixture of an organohydrogensiloxane, a polyoxyalkylene compound, a liquid, saturated, polar, polyol, solvent having a boiling point of greater than 175.degree. C., and optionally a salt of a carboxylic acid as a reaction promoter, maintaining said mixture in an inert atmosphere and adding to said mixture a catalytic amount of a noble metal hydrosilylation catalyst, reacting the mixture at a temperature below about 92.degree. C., and recovering the surfactant in admixture with residual polyol solvent.
Silicone compounds suitable for use as defogging compositions or as anti-misting agents have also been described. For example, Maruyama et al. in U.S. Pat. No. 4,567,221 disclose water resistant compositions which contain a modified polyvinyl alcohol having a silyl group in the molecule and an organic substance, useful as compositions for treating inorganic materials and defogging compositions. Japanese Patent Application Laid-open Nos. 27495/1978, 27496/1978, and 27497/1978 disclose thermosetting resin compositions giving anti-misting coatings, one prepared by hydrolysing a mixture of aminosilane and vinylsilane, or by further adding a copolymer of hydrophilic vinyl monomers, or a transparent thermosetting resin composition prepared from a mixture of an aminoalkoxysilane, a mercapto-propyl trimethoxysilane, and a vinyl copolymer.
Japanese Patent Application Laid-open No. 23748/1977 discloses anti-misting agents prepared by adding ethylene glycol and/or glycerol to polyethylene glycol, heating, and then addition of a silicone type water repellant and molding.
However, none of these references discloses a method of preparing an aerosol suppressant composition comprising reacting an organosilicon compound, an oxyalkylene containing compound, and a catalyst which, when added to curable silicone coatings, reduces the amount of mist in high speed coating processes.